This invention relates to a method and apparatus for connecting an internally threaded fastener element to a wall by cold expanding a non-threaded tubular portion of the fastener element within an opening in the wall and providing the fastener element with wall contacting flanges on both sides of the wall.
The aerospace industry utilizes a fastener that is in the nature of a tubular rivet with internal threads. It can be installed in seconds into an opening in a wall from one side of the wall. No finishing work is required once the fastener is installed. It is ready for use with clean threads available for screw attachment. This tubular rivet has a flange on one end. The opposite end is inserted into the opening in the wall and the tubular rivet is pushed into the opening until the flange is against the wall. A rod with a threaded end is then inserted into the tubular rivet from the flange side of the wall and is connected to threads inside the tubular rivet. Then, a hand or power tool is operated to pull on the rod. This causes a wall portion of the tubular rivet on the second side of the wall to bulge out radially and form a second flange that is moved into tight engagement with the second side of the wall. A tubular rivet system of this type is currently provided by RIVNUT(copyright) Engineered Products, Inc. of Kendallville, Ind. An early form of this type of system is disclosed by U.S. Pat. No. 2,384,347, granted Sep. 4, 1945, to Michael Schultz. A problem with known tubular rivets is that they often rotate in the opening when torque is applied to a screw that is connected to the tubular rivet after it has been installed.
It is known to install a nut holder on a wall at the location of an opening in the wall and then connect a nut to the installed nut holder. A tubular stem portion of the nut holder is inserted into the opening in the wall and is then radially expanded to connect it to the wall and also cold work the wall material surrounding the opening for fatigue life enhancement. Then the nut is connected to the nut holder to provide bolt receiving threads. Examples of this type of system are disclosed by U.S. Pat. No. 5,096,349, granted Mar. 17, 1992, to Michael A. Landy, Roger T. Bolstad, Charles M. Copple, Darryle Quincey, Eric T. Esterbrook, Leonard F. Reid and Louis A. Champoux, and by U.S. Pat. No. 5,468,104, granted Nov. 21, 1995, to Leonard F. Reid and Charles M. Copple. The radial expansion locks the nut holder against rotating but these systems require attachment of a nut to provide the wall insert with the internal threads.
There is a need for a method and apparatus for installing a fastener element with internal threads in an opening in a wall in such a way that the tubular rivet is restrained against rotating in response to a bolt being threaded into the fastener element. An object of the present invention is to provide such a method and apparatus.
According to an aspect of the invention, an internally threaded fastener element is inserted into a close fitting circular opening in a wall and is moved axially inwardly until a flange at its trailing end makes contact with the wall where it immediately surrounds the opening. The fastener element is provided with a tubular end portion that is positioned inside the opening when the flange is in contact with the wall. The fastener element is also provided with an annular sidewall region of reduced thickness that is positioned on the second side of the wall axially between the opening in the wall and the internal threads in the fastener element. A threaded end portion of a rod is inserted into the fastener element from the first side of the wall and is rotated to connect it to the internal threads in the fastener element. A tubular mandrel is provided in a surrounding relationship to the rod on the first side of the wall. The tubular mandrel has an outer diameter that is larger than a center opening in the tubular portion of the fastener element that is within the opening in the wall. The tubular mandrel also has an end portion that is adapted to enter into the center opening from the first side of the wall. The rod is retracted axially relatively into and through the mandrel, to cause the annular sidewall region of reduced thickness to buckle and form a second flange and move the second flange against the second side of the wall, so that the wall is held between the two flanges. Also according to the invention, the mandrel is moved axially into the center opening of the tubular portion of the fastener element that is in the opening. The mandrel is sized so that as it moves into the center opening it radially expands the tubular portion of the fastener an amount sufficient to firmly connect it to the sidewall of the wall opening and hold it against rotation in response to torque applied by a screw that this later screwed into the fastener element.
According to a further aspect of the invention, a motor is provided for rotating the rod for threading the threaded end portion of the rod into and unthreading it out from the internal threads in the fastener element.
Another aspect of the invention is to radially expand a tubular member within an opening in a wall, for connecting the member to the wall, by pushing an expansion mandrel axially into a center opening in the tubular portion while holding the tubular portion in the wall. The member is provided with a flange at its trailing end. The member is inserted into the opening in the wall and pushed forwardly until the flange contacts the wall. The member is held in the opening by inserting a rod through the mandrel, engaging the member with the rod on the second side of the opening, and pulling the rod while at the same time contacting the perimeter of the center opening with the mandrel.
According to another aspect of the invention, a tool is provided for installing into a wall opening, a fastener element having a tubular first end portion that is sized to fit snugly within the wall opening, a center opening having an entrance, and an end flange surrounding the entrance. The tool comprises an elongated rod having a longitudinal axis. The rod is adapted to be rotated about the longitudinal axis. The rod also has an outer end portion that is adapted to be inserted into the center opening and be connected to the fastener element. The tool includes a tubular mandrel that projects axially. A center opening extends through the mandrel and the rod extends through the center opening. The mandrel has an outside diameter that is larger than the center opening in the fastener element. The mandrel is movable axially back and forth along the rod, towards and away from the outer end portion of the rod.
The tool may also comprise an elongated tubular member within the housing that is movable back and forth endwise relative to the housing. This tubular member has an outer end and the mandrel is at this outer end. The elongated rod extends endwise from its inner end through the elongated tubular member and the tubular mandrel to its free end. Preferably, there is a piston inside the housing that is connected to the elongated tubular member and there are a pair of fluid chambers in the housing, one on each side of the piston. Fluid introduction into and removal from the fluid chambers cause the back and forth movement of the tubular member.
The tool may also comprise a tubular nose piece that surrounds and is concentric with the elongated tubular member. The tubular nose piece is movable endwise back and forth longitudinally along the elongated tubular member. Preferably also, there is a second piston inside of the housing that is connected to the tubular nose piece, and there is a pair of fluid chambers in the housing, one on each side of the second piston. Fluid introduction into and removal from the fluid chambers cause the back and forth movement of the tubular member.
These and other advantages, objects, and features will become apparent from the following best mode description, the accompanying drawings, and the claims, which are all incorporated herein as part of the disclosure of the invention.